During various Navy test and practice operations, practice torpedoes are routinely fired at ships, submarines or models thereof. Although these practice torpedoes are designed for last minute impact avoidance, they nevertheless occasionally strike their intended target. It is therefore of interest to know `a priori` what kind of impact forces may result in order to predict the consequences of such an impact. Accordingly, it is desirable to develop an accurate force history spanning the time that a torpedo impacts a target.
Upon impact, torpedoes experience large inelastic deformation and often fracture. In addition, equipment internal to the torpedo may break loose and strike the forward portion of the torpedo, thereby modifying the delivered impact load. Thus, reliable impact force histories cannot in general be predicted entirely by analytical means. In the past, impact force histories were obtained from full scale tests carried out on operational boats in drydock. Alternatively, large single compartment models containing simulated equipment were impacted and various schemes were used to reconstitute the impact force histories. However, the schemes used did not provide for an accurate definition of the higher frequency impact response components (on the order of 1-10 kHz) generated by the impact. In very general terms, the higher frequency components occur during the first few milliseconds after impact while lower frequency components (less than approximately 1 kHz) are associated with the remainder of the event. An additional drawback is that the expense associated with using operational boats or large scale models greatly inhibits the amount of testing and development defining torpedo impact forces.